Photo: This unusual Darrieus "egg-beater" wind turbine rotates about a vertical axis, unlike a normal turbine with a horizontal rotor. Its main advantage is that it can be mounted nearer to the ground, without a tower, which makes it cheaper construct. It can also capture wind coming from any direction without using things like pitch and yaw motors, which makes it simpler and cheaper.
Even so, turbines like this suffer from a variety of other problems and are quite inefficient at capturing energy, so they're very rare. Photo by courtesy of US Department of Energy. At first sight, it's hard to imagine why anyone would object to clean and green wind turbines—especially when you compare them to dirty coal-fired plants and risky nuclear ones, but they do have some disadvantages.
One of the characteristics of a wind turbine is that it doesn't generate anything like as much power as a conventional coal, gas, or nuclear plant. A typical modern turbine has a maximum power output of about 2 megawatts MW , which is enough to run 2kW electric toasters simultaneously—and enough to supply about homes , if it produces energy about 30 percent of the time. The world's biggest offshore wind turbines can now make 8 megawatts, since winds are stronger and more persistent out at sea, and power about homes.
In theory, you'd need 2MW turbines to make as much power as a really sizable MW or 2GW coal-fired power plant or a nuclear power station either of which can generate enough power to run a million 2kW toasters at the same time ; in practice, because coal and nuclear power stations produce energy fairly consistently and wind energy is variable, you'd need rather more. If a good nuclear power plant operates at maximum capacity 90 percent of the time and a good, brand new, offshore wind farm manages to do the same 45 percent of the time , you'd need twice as many wind turbines to make up for that.
Ultimately, wind power is variable and an efficient power grid needs a predictable supply of power to meet varying demand. In practice, that means it needs a mixture of different types of energy so supply can be almost percent guaranteed. Some of these will operate almost continually like nuclear , some will produce power at peak times like hydroelectric plants , some will raise or lower the power they make at short notice like natural gas , and some will make power whenever they can like wind.
Wind power can't be the only form of supply—and no-one has ever pretended that. As we've just seen, you can't jam a couple of thousand wind turbines tightly together and expect them to work effectively; they have to be spaced some distance apart typically 3—5 rotor diameters in the "crosswind" direction, between each turbine and the ones either side, and 8—10 diameters in the "downwind" direction, between each turbine and the ones in front and behind.
Put these two things together and you arrive at the biggest and most obvious disadvantage of wind power: it takes up a lot of space. If you wanted to power an entire country with wind alone which no-one has ever seriously suggested , you'd need to cover an absolutely vast land area with turbines.
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You could still use almost all the land between the turbines for farming; a typical wind farm removes less than 5 percent of land from production for the turbine bases, access roads, and grid connections. You could mount turbines out at sea instead, but that raises other problems and costs more.
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Even onshore, connecting arrays of wind turbines to the power grid is obviously a bigger hurdle than wiring up a single, equivalent power plant. Some farmers and landowners have objections to new power lines, though many earn handsome profits from renting out their land potentially with a guaranteed income for a quarter of a century , most of which they can continue to use as before.
On the plus side, wind turbines are clean and green: unlike coal stations, once they're constructed, they don't make the carbon dioxide emissions that are causing global warming or the sulfur dioxide emissions that cause acid rain a type of air pollution. Once you've built them, the energy they make is limitless and except for spare parts and maintenance free over a typical lifetime of 25 years.
That's even more of an advantage than it sounds, because the cost of running conventional power plants is heavily geared to risky things like wholesale oil and gas prices and the volatility of world energy markets. Wind turbine towers and nacelles contain quite a bit of metal , and concrete foundations to stop them falling over a typical turbine has parts in total , so constructing them does have some environmental impact. Even so, looking at their entire operating lifespan, it turns out that they have among the lowest carbon dioxide emissions of any form of power generation, significantly lower than fossil-fueled plants, most solar installations, or biomass plants.
Now nuclear power plants also have relatively low carbon dioxide emissions, but wind turbines don't have the security, pollution, and waste-disposal problems many people associate with nuclear energy, and they're much quicker and easier to construct. They're also much cheaper, per kilowatt hour of power they produce: half the price of nuclear and two thirds the price of coal according to figures quoted by Milligan et al.
According to the Global Wind Energy Council, a turbine can produce enough power in 3—6 months to recover the energy used throughout its lifetime constructing, operating, and recycling it. Some people worry that because wind is very variable, we might suddenly lose all our electricity and find ourselves plunged into a "blackout" a major power outage if we rely on it too much.
The reality of wind is quite different. Wherever you live, your power comes from a complex grid network of intricately interconnected power-generating units ranging from giant power plants to individual wind turbines. Utility companies are highly adept at balancing power generated in many different places, in many different ways, to match the load the total power demand as it varies from hour to hour and day to day.
The power from any one wind turbine will fluctuate as the wind rises and falls, but the total power produced by thousands of turbines, widely dispersed across an entire country, is much more regular and predictable. For a country like the UK, it's pretty much always windy somewhere. As Graham Sinden of Oxford University's Environmental Change Institute has shown, low wind speeds affect more than half the country for only 10 percent of the time; for 60 percent of the time, only 20 percent of the UK suffers from low wind speeds; and only for one hour per year is 90 percent of the UK suffering low speeds Sinden , figure 7.
In other words, having many wind turbines spread across many different places guarantees a reasonably steady supply of wind energy virtually all year round. Photo: You can put lots of turbines together to make a wind farm, but you need to space them out to harvest the energy effectively. Combining the output from many wind farms in many different areas produces a smoother and more predictable power supply.
It's also worth bearing in mind that wind is relatively predictable several days in advance so it's easy for power planners to take account of its variability as they figure out how to make enough power to meet expected demands. Opponents of wind power have even suggested that it might be counter-productive, because we'd need to build extra backup coal, nuclear, biomass, or hydro plants or some way of storing wind-generated electricity for those times when there's not enough wind blowing. That would certainly be true if we made all our energy from one, single mega-sized wind turbine—but we don't!
In reality, even countries that have large supplies of wind energy have plenty of other sources of power too; as long as wind power is making less than half of a country's total energy, the variability of the wind is not a problem. Denmark, for example, makes 20 percent of its electricity—and meets 43 percent of its peak load—with wind; Eric Martinot's article "How is Denmark Integrating and Balancing Renewable Energy Today?
In practice, every country's electricity has always come from a mixture of different energy sources, and the ideal mix varies from one country to another for geographical, practical, and political reasons. Photo: How pumped storage works: When there's lots of cheap electricity about at night or when the wind is blowing , water is pumped up the mountain to the high-level lake at low cost.
When electricity is more expensive and valuable in the day, at peak times , the water drains from the high lake to the low one, powering a hydroelectric turbine. Wind could play a bigger part in the future if we could find cost-effective ways of storing electricity produced on windy days for times when there's little or no wind to harvest. One tried and tested possibility is pumped storage : low-price electricity is used to pump huge amounts of water up a mountain to a high-level lake, ready to be drained back down the mountain, through a hydroelectric turbine, at times of high demand when the electricity is more valuable.
In effect, we store electricity as gravitational potential energy, which we can do indefinitely, and turn it back to electricity when it suits us. Batteries could also be a contender—if we had enough of them. There have been suggestions about using a fleet of electric cars as a giant collective battery , for exactly this purpose, but even large-scale batteries hooked up to individual wind farms could be very helpful.
Statoil, for example, plans to install a huge wind-powered battery called BatWind in Scotland. Flywheels heavy, low-friction wheels that store energy as they spin are another possibility. It certainly has a part to play, but how big a part depends on where in the world you are and whether there are better alternatives suited to your local geography. In sunny Australia, for example, solar would probably be cheaper.
In countries that have windy winters when electricity demand is at its highest , wind turbines could be a strong contender; on August 11, , for example, wind turbines in windy Scotland produced enough energy to power the whole country , while for a brief period in one week of November , wind provided a third of the UK's entire electricity.
Countries with lots of fossil-fueled plants and no plans to retire them soon might find investments in carbon capture and storage scrubbing the carbon dioxide from the emissions of coal and other fossil plants a wise option, though that remains a largely unproven technology. Ultimately, it's a political choice as well as a scientific one. In Germany, where people have strong opposition to nuclear power, there have been huge investments in wind energy.
Denmark, another European country, plans to move to percent renewable energy with a massive commitment to wind.
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Although China is investing heavily in wind power , it still makes about three quarters of its electricity from coal. In short, while the growth of wind power is impressive, it still plays a relatively small part, overall, in providing the world's electricity.
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Chart: Which countries are making the most of their wind? It's no surprise to find the biggest countries China, the United States, and India among them topping the list of countries with the most installed wind capacity, measured in gigawatts.
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But if we measure installed capacity per capita, we get this very different chart. Now European countries such as Denmark, Sweden, and Germany lead the pack, the United States is 11th, China manages only 20th place, and India comes in at number Drawn by Explainthatstuff. These were the most recent datasets available at the time this article was last updated in August Photo: Micro power to the people!
This small, mast-mounted Rutland Windcharger is designed to trickle-charge 12V and 24V batteries, such as those used in small boats, far from the grid. If small is beautiful, micro-wind turbines—tiny power generators of about 50— W capacity, perched on a roof or mast—should be the most attractive form of renewable energy by far. They're certainly very widely used for all kinds of portable power, typically for recharging batteries in things like yachts and canal boats, and for powering temporary traffic lights and road signs. Some manufacturers have pushed micro-wind technology aggressively, hinting that people could make big savings on electricity bills, and benefit the environment, by putting a little turbine on their roof to feed energy into the national power grid.
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The reality is a bit different: micro-turbines linked to the grid do indeed bring economic and environmental benefits if they're sited in reliably windy areas, but they're less helpful in towns and cities where buildings make "energy harvesting" more of a challenge and there's much more turbulence from obstructions. So are micro-wind turbines really worth the investment? How do they compare with their big brothers? These figures are simply designed to give a rough comparison of the differences between large-scale and micro-wind turbines.
Bear in mind that there's a huge variety of micro-turbines. If you want to build your own micro-wind turbine, what do you need? The first thing to bear in mind is that small wind turbines spin at dangerously high speeds, so technical skill and safety are paramount: ideally, get your turbine installed by a professional. Apart from the turbine itself, you also typically need a piece of electrical equipment called an inverter which converts the direct-current electricity produced by the turbine's generator into alternating current you can use in your home and appropriate electrical cabling.
Your turbine will also need either a connection into the grid supply or batteries to store the energy it produces. Photo: Although micro-wind turbines on homes have proved controversial, they definitely have their place. Here's the Rutland Windcharger from our top photo helping to charge the batteries in a go-anywhere, portable highway construction sign. My woodworking skills are pretty basic and making your own blades requires some pretty good attention to detail.
So I decided to save myself the time and effort of making blades and just buy a ready made set. There are lots of guides and tutorials for blade-making online. Hugh Piggot even offers a nice table of useful figures for different blade diameters in Windpower Workshop. Now, there is a lot to consider when buying blades. First and foremost, consider the power you are taking from the wind. This is based mostly on the diameter of your wind turbine blades. A wind turbine steals energy from the wind by slowing it down as it passes through the blades and makes the rotor turn.
This is all laid out mathematically by the Betz' Limit. These calculations show the maximum amount of energy that is possible to be extracted from the wind, though they do not account for losses in generator efficiency It isn't so simple as bigger blades equals more power, though! No, no, no. What is most important is that you match the blades to your generator.
Generators are designed to start producing usable electricity the voltage you want at a certain RPM. This is where the Tip Speed Ratio comes in.
Basically, you want to have blades that provide that RPM at the most typical wind speed you'll be experiencing. Sound complicated? It is, kind of. I would recommend using it as a rule of thumb. There really is a lot to blade making as well as blade theory, but that should give you some good general insight into what you're trying to accomplish. As for me, I bought my blades from a website called Magnet4less no 's'. At first I actually bought the wrong size blades thinking I could get away with a bigger diameter, but alas, physics wins again Some of the pictures may have these first blades in them.
I eventually folded and bought the 6. However, I would NOT recommend buying these blades again. They have terrible reviews from wind power people around the country and with my personal experience they look like the angle of attack just isn't enough to spin up high RPMs. This is the part where I suggest another retailer but, to tell you the truth, I really don't know of one.
Homebrew wind turbines enthusiasts seem to be mostly but I could be corrected out of luck for high quality universal blades with different diameters. I suppose you could use a pair of replacement blades from another commercial turbine assuming they are to your needs. Other references! I don't recommend PVC blades for a turbine like mine, though. Now that most of the construction of the actual wind turbine piece is complete, you'll have to decide on a place to put the beast! Obviously a good spot with lots of wind and few obstructions is optimal.
Most DIY wind power enthusiasts recommend that your tower be 30 feet above the nearest obstruction within a foot radius. In other words, pretty much as high and in the most open area as you can get it. Selecting a location and tower is difficult, there is no doubt about it. It's hard on your wallet and your time. The biggest concern when putting up a tower should always be safety. This is a homebrew turbine and could run into problems that we can't quite predict, so a little extra safety is always good.
Be aware that if your blades fail at high RPMs if they will fly quite a distance and could pose a threat to nearby houses or cars. A basic run down of the tower options available. Uses guy wires and a hinge at the bottom of the tower and can be welded together with the correct pipe. The problem with this is that it must be climbed to do anything to the windmill. Many people do not feel safe doing this and many people have been hurt from falling off stationary towers like this. Use extreme caution and a safety harness to work on top of one of these towers. I was fortunate enough to receive a free 30 foot lattice tower from an airport.
It was once used for a rotating beacon and should be strong enough for my small wind turbine. I had to add to the top of it about 5 feet to attach the wind turbine with enough clearance for the blades to move around when the machine furls. For support, we welded gussets onto a piece of 2 inch pipe and attached it to the top of the tower. Then I took a piece of schedule 80 pipe to a machine shop and had it turned down on the lathe so it would act nicely as the yaw bearing.
We leveled it on the tower and placed some set screws in so it could be welded in place. This piece is important because, if it comes loose, the whole turbine could fall off or the blades could hit the tower! Welding was completed with a DC arc welder. I'm still not terrific at welding by any means, but it's a great skill to learn. Before I made the welds on the tower, I did some practicing on some scrap pieces I acquired from a metal shop.
That's another thing you find while trying to learn to weld - people in metal shops are usually quite friendly and willing to help out. If you're thinking about learning but are lacking material to practice on, ask around - what many might consider junk could be very useful to you. At first I was going to build my own controller, as I have shown in the pictures below.
The project shifted locations, though, and I decided to charge a battery instead of heat water, so I decided against it. I did have a rough idea of what I was going to do, but I think not making the controller on my first turbine was probably a good decision. Things can get dangerous if your controller fails and lets your turbine run away at reckless RPMs.
Also, believe it or not, electrical permits prefer stuff that's UL listed Instead of heating water, I decided to charge a 12 volt battery that would be hooked up to a light. This cut down on costs, logistics, and other restrictions that made it a bit easier to install. One regulates the charge coming in and the other watches the charge level of the battery to ensure it is not overcharged it can't do both at the same time. I have a 12 volt dump load that is a water heating element, rated for watts.
I used a three phase disconnect switch as the "brake" on the wind turbine. When the switch is closed, all three phases of the wind turbine are shorted out and it will slow itself down. I also used a watt modified sine wave inverter to run the light. The light has a photoelectric eye on it and is wired up to turn on at night. Before programming the controller, it is important to see what kind of power output you can achieve with your generator.
This will help you determine what RPM is optimal for you to run at and how that affects the pitch of the blades. Now, a lot of people have a lathe, a tachometer and a bunch of other fancy tools to test their generators. Well, I am a bit less fortunate and do not have those available to me. So, instead, I made a simple jig to spin up my generator using an electric drill. I cut a notch in a small piece of wood and shaped it as a trapezoid to avoid all the holes for the bolts. On the other side, I screwed through a hole in the metal into the wood to hold it in place. The other two planned attachment places were too close to the edge to take a screw, so I drilled a couple of small holes and used small zip-ties.
Surprisingly, this setup is pretty solid. The piece of wood doesn't act like it's going anywhere and those zip-ties are nice and snug. Now, with all of these funny angles and stuff, it's hard to find the exact center of the rotor. I did the best I could to eyeball it and I drilled two more long screws partway into the wood on either side of the center.
Then use an allen wrench with a T-handle on it that is long enough to touch these two screws. These screws will take the torque from the drill to spin up the generator. To gather data on the output of the generator, you'll need a few things.
Mainly a couple of good multimeters, a test load, and some way to read the RPM. I attempted to use the equipment in my physics lab and Datastudio to measure the frequency of the AC current, then I tried to work backwards to figure out the RPM of the generator.
This method, however I kept getting readings that were very off. Despite the pretty graphs the equipment was generating, I would not recommend trying to use this method for measuring RPM. Many people use fancy bicycle tachometers with good results. Luckily my physics teacher is an avid bicycle rider and had a box full of old bicycle computers that he let me try out. I found one with an RPM counter and zip tied a neodymium magnet onto one side of the testing jig. Then I used a ring stand and a clamp to hold the sensor in place.
Now I could read the RPMs fairly easily, although they didn't update immediately this method was far more accurate. I would highly suggest if you want accurate readings to get a decent tachometer or a bicycle computer with an RPM setting. I was also able to use Datastudio to measure the DC voltage coming off the generator.
The equipment only measured up to 10 volts DC, so I used a simple voltage divider to scale down the voltage being read by the computer. So the actual voltage on the graph was 12 times voltage read by the computer. See pictures for the schematic. Also, I needed to flatten out the DC coming off the rectifier. To do this I used a big capacitor in parallel to flatten out the voltage spikes, giving a more accurate DC voltage reading.
You have to watch a lot of things when you spin up the generator. It's hardest to measure voltage, current and rpm while still holding onto the drill. For my test load, I used six 18 ohm 25 watt resistors in parallel for a total of 3. Since my tower was 36 feet tall and in a triangular lattice structure 18 inches per side , I knew I would need a big sono tube to support it. After googling, reading, and asking a certified wind turbine installer, I settled on a 2 foot diameter, 6 foot tall sono tube. It's not a bad idea to consider the soil you'll be digging into, as some places may need more of a footing just to be sure.
Luckily for me, since this project was being funded, we were able to talk the local concrete place into doing it all for free. They even dug a hole and centered a piece of pipe in the casing for us. Also, consider how you want to attach your tower to the base. My first thought was to have tree bolts sticking up from the base one for each leg , but the wind turbine installer suggested something different. He suggested we put a piece of plate or something on the bottom with a hole in it, then have one solid pipe or piece of bar stock in the base and slide the tower down over.
This does a couple of things. Firstly, it allows the tower to move, which is nice, and secondly, it reduces stress on the concrete base because the pipe is centered on the casting. I decided to use three guy anchors, one for each corner of the tower. These anchors should be evenly spaced and as close to equidistant from the tower as you can get. I chose a 22 foot guy radius, meaning the distance from the center of the base to the guy anchor hook was 22 feet. This figure was based off of some other towers I had read about as well as the suggestion of the wind turbine installer.
It's a good idea to get a friend to help you put in the anchors, since pouring concrete by yourself isn't much fun. Taste the Tradition. Book Now. Wind Rose Resort. Book Now Go Virtual Tour. Wind Rose Resort by Karisma Highlights True Colors of the Beach The sparkling unspoiled Adriatic Sea changes tones from cerulean to emerald.